Twenty-five years ago on March 24, 2001, Apple launched Mac OS X Cheetah, marking the beginning of a new era for the Mac. The operating system, which would power Apple's computers for the next 19 years, represented a dramatic shift from the classic Mac OS that had been in use since 1984. While the initial release was slow and buggy, it laid the foundation for the modern macOS we know today.

OS X emerged after years of failed attempts by Apple to create a revolutionary new operating system. Throughout the 1990s, projects like Pink, Taligent, Copland, and Gershwin all fell short. The breakthrough came when Apple acquired NeXT in 1997, bringing Steve Jobs back to the company and gaining access to NeXTSTEP, the technology that would become OS X. This acquisition proved to be one of the most pivotal moments in Apple's history.

Steve Jobs envisioned OS X as having the best "internal plumbing" of any operating system, with "killer graphics" and internet connectivity at its core. The operating system introduced groundbreaking features like the Dock, Mail, TextEdit, and Contacts, while the Quartz graphics engine based on PDF technology enabled universal PDF creation across all apps. Though the Aqua interface evolved over time, OS X's core architecture remained consistent through successive updates like Puma, Jaguar, Panther, and eventually macOS Big Sur, which marked the transition to Apple Silicon.